Motor control unit, control method, and power assembly

Abstract

A motor control unit includes a three-phase full-bridge three-level inverter circuit and a control apparatus. The three-phase full-bridge three-level inverter circuit includes a vertical bridge circuit and a horizontal bridge circuit. A current capacity of a switching transistor in the vertical bridge circuit is greater than or equal to a maximum current of a motor. A current capacity of a switching transistor in the horizontal bridge circuit is less than the current capacity of the switching transistor in the vertical bridge circuit. The control apparatus is configured to control the switching transistor in the horizontal bridge circuit based on torque of the motor, a current output by an output terminal of the vertical bridge circuit, a temperature of the switching transistor in the horizontal bridge circuit, and a terminal voltage of the switching transistor in the horizontal bridge circuit.

What is claimed is: 
     
         1 . A motor control unit, comprising:
 a three-phase full-bridge three-level inverter circuit; and   a control apparatus, wherein the three-phase full-bridge three-level inverter circuit comprises:
 a vertical bridge circuit; and 
 a horizontal bridge circuit; a current capacity of a switching transistor in the vertical bridge circuit is greater than or equal to a maximum current of a motor, and a current capacity of a switching transistor in the horizontal bridge circuit is less than the current capacity of the switching transistor in the vertical bridge circuit; and 
   the control apparatus is configured to control the switching transistor in the horizontal bridge circuit based on torque of the motor, a current output by an output terminal of the vertical bridge circuit, a temperature of the switching transistor in the horizontal bridge circuit, and a terminal voltage of the switching transistor in the horizontal bridge circuit.   
     
     
         2 . The motor control unit according to  claim 1 , wherein the control apparatus is further configured to:
 disable the switching transistor in the horizontal bridge circuit when the torque of the motor is greater than a first torque threshold, the current output by the output terminal is greater than a first overcurrent threshold, the temperature of the switching transistor in the horizontal bridge circuit is greater than a first temperature threshold, or the terminal voltage of the switching transistor in the horizontal bridge circuit is greater than a first voltage threshold; or   enable the switching transistor in the horizontal bridge circuit when the torque of the motor is not greater than a first torque threshold, the current output by the output terminal is not greater than a first overcurrent threshold, the temperature of the switching transistor in the horizontal bridge circuit is not greater than a first temperature threshold, or the terminal voltage of the switching transistor in the horizontal bridge circuit is not greater than a first voltage threshold.   
     
     
         3 . The motor control unit according to  claim 1 , wherein the control apparatus is further configured to:
 control the switching transistor in the vertical bridge circuit based on the torque of the motor, the current output by the output terminal, a rotational speed of the motor, a temperature of the switching transistor in the vertical bridge circuit, and a terminal voltage of the switching transistor in the vertical bridge circuit.   
     
     
         4 . The motor control unit according to  claim 2 , wherein the control apparatus is further configured to:
 control the switching transistor in the vertical bridge circuit based on the torque of the motor, the current output by the output terminal, a rotational speed of the motor, a temperature of the switching transistor in the vertical bridge circuit, and a terminal voltage of the switching transistor in the vertical bridge circuit.   
     
     
         5 . The motor control unit according to  claim 3 , wherein the control apparatus is further configured to:
 when the torque of the motor is greater than a second torque threshold or the current output by the output terminal is greater than a second overcurrent threshold,   when the rotational speed of the motor is less than or equal to a rotational speed threshold, the temperature of the switching transistor in the vertical bridge circuit is greater than a second temperature threshold, or the terminal voltage of the switching transistor in the vertical bridge circuit is greater than a second voltage threshold, disable the switching transistor in the vertical bridge circuit; or   when the rotational speed of the motor is greater than a rotational speed threshold, the temperature of the switching transistor in the vertical bridge circuit is not greater than a second temperature threshold, and the terminal voltage of the switching transistor in the vertical bridge circuit is not greater than a second voltage threshold, conduct an upper-half-bridge switching transistor or a lower-half-bridge switching transistor in the vertical bridge circuit; and   when the torque of the motor is less than or equal to a second torque threshold or the current output by the output terminal is less than or equal to a second overcurrent threshold, enable the switching transistor in the vertical bridge circuit.   
     
     
         6 . The motor control unit according to  claim 1 , wherein the control apparatus is further configured to:
 after enabling or disabling the switching transistor in the horizontal bridge circuit, adjust a duty cycle of a pulse width modulation control signal, so that a voltage output by the output terminal remains unchanged.   
     
     
         7 . A control method for a motor control unit, applied to a motor control unit, wherein the motor control unit comprises a three-phase full-bridge three-level inverter circuit and a control apparatus, wherein the three-phase full-bridge three-level inverter circuit comprises a vertical bridge circuit and a horizontal bridge circuit; a current capacity of a switching transistor in the vertical bridge circuit is greater than or equal to a maximum current of a motor, and a current capacity of a switching transistor in the horizontal bridge circuit is less than the current capacity of the switching transistor in the vertical bridge circuit; and the control method comprises:
 controlling a switching transistor in a horizontal bridge circuit based on torque of a motor, a current output by an output terminal of a vertical bridge circuit in a three-phase full-bridge three-level inverter circuit, a temperature of the switching transistor in the horizontal bridge circuit in the three-phase full-bridge three-level inverter circuit, and a terminal voltage of the switching transistor in the horizontal bridge circuit.   
     
     
         8 . The control method according to  claim 7 , further comprising:
 disabling the switching transistor in the horizontal bridge circuit when the torque of the motor is greater than a first torque threshold, the current output by the output terminal is greater than a first overcurrent threshold, the temperature of the switching transistor in the horizontal bridge circuit is greater than a first temperature threshold, or the terminal voltage of the switching transistor in the horizontal bridge circuit is greater than a first voltage threshold; or   enabling the switching transistor in the horizontal bridge circuit when the torque of the motor is not greater than a first torque threshold or the current output by the output terminal is not greater than a first overcurrent threshold, the temperature of the switching transistor in the horizontal bridge circuit is not greater than a first temperature threshold, and the terminal voltage of the switching transistor in the horizontal bridge circuit is not greater than a first voltage threshold.   
     
     
         9 . The control method according to  claim 7 , further comprising:
 controlling a switching transistor in the vertical bridge circuit based on the torque of the motor, the current output by the output terminal, a rotational speed of the motor, a temperature of the switching transistor in the vertical bridge circuit, and a terminal voltage of the switching transistor in the vertical bridge circuit.   
     
     
         10 . The control method according to  claim 9 , further comprising:
 when the torque of the motor is greater than a second torque threshold or the current output by the output terminal is greater than a second overcurrent threshold,   when the rotational speed of the motor is less than or equal to a rotational speed threshold, the temperature of the switching transistor in the vertical bridge circuit is greater than a second temperature threshold, or the terminal voltage of the switching transistor in the vertical bridge circuit is greater than a second voltage threshold, disabling the switching transistor in the vertical bridge circuit; or   when the rotational speed of the motor is greater than a rotational speed threshold, the temperature of the switching transistor in the vertical bridge circuit is not greater than a second temperature threshold, and the terminal voltage of the switching transistor in the vertical bridge circuit is not greater than a second voltage threshold, conducting an upper-half-bridge switching transistor or a lower-half-bridge switching transistor in the vertical bridge circuit; and   when the torque of the motor is less than or equal to a second torque threshold or the current output by the output terminal is less than or equal to a second overcurrent threshold, enabling the switching transistor in the vertical bridge circuit.   
     
     
         11 . The control method according to  claim 7 , further comprising:
 after the switching transistor in the horizontal bridge circuit is enabled or disabled, adjusting a duty cycle of a pulse width modulation control signal, so that a voltage output by the output terminal remains unchanged.   
     
     
         12 . A power assembly, comprising a motor control unit, a direct current power supply, and a motor, wherein the motor control unit comprises a three-phase full-bridge three-level inverter circuit and a control apparatus, wherein the three-phase full-bridge three-level inverter circuit comprises a vertical bridge circuit and a horizontal bridge circuit; a current capacity of a switching transistor in the vertical bridge circuit is greater than or equal to a maximum current of a motor, and a current capacity of a switching transistor in the horizontal bridge circuit is less than the current capacity of the switching transistor in the vertical bridge circuit; and
 the control apparatus is configured to control the switching transistor in the horizontal bridge circuit based on torque of the motor, a current output by an output terminal of the vertical bridge circuit, a temperature of the switching transistor in the horizontal bridge circuit, and a terminal voltage of the switching transistor in the horizontal bridge circuit;   wherein the motor control unit is configured to: convert a direct current output by the direct current power supply into an alternating current, supply power to the motor, and control a rotational speed of the motor.   
     
     
         13 . The power assembly according to  claim 12 , wherein the control apparatus is further configured to:
 disable the switching transistor in the horizontal bridge circuit when the torque of the motor is greater than a first torque threshold, the current output by the output terminal is greater than a first overcurrent threshold, the temperature of the switching transistor in the horizontal bridge circuit is greater than a first temperature threshold, or the terminal voltage of the switching transistor in the horizontal bridge circuit is greater than a first voltage threshold; or   enable the switching transistor in the horizontal bridge circuit when the torque of the motor is not greater than a first torque threshold, the current output by the output terminal is not greater than a first overcurrent threshold, the temperature of the switching transistor in the horizontal bridge circuit is not greater than a first temperature threshold, or the terminal voltage of the switching transistor in the horizontal bridge circuit is not greater than a first voltage threshold.   
     
     
         14 . The power assembly according to  claim 12 , wherein the control apparatus is further configured to:
 control the switching transistor in the vertical bridge circuit based on the torque of the motor, the current output by the output terminal, a rotational speed of the motor, a temperature of the switching transistor in the vertical bridge circuit, and a terminal voltage of the switching transistor in the vertical bridge circuit.   
     
     
         15 . The power assembly according to  claim 13 , wherein the control apparatus is further configured to:
 control the switching transistor in the vertical bridge circuit based on the torque of the motor, the current output by the output terminal, a rotational speed of the motor, a temperature of the switching transistor in the vertical bridge circuit, and a terminal voltage of the switching transistor in the vertical bridge circuit.   
     
     
         16 . The power assembly according to  claim 14 , wherein the control apparatus is further configured to:
 when the torque of the motor is greater than a second torque threshold or the current output by the output terminal is greater than a second overcurrent threshold,   when the rotational speed of the motor is less than or equal to a rotational speed threshold, the temperature of the switching transistor in the vertical bridge circuit is greater than a second temperature threshold, or the terminal voltage of the switching transistor in the vertical bridge circuit is greater than a second voltage threshold, disable the switching transistor in the vertical bridge circuit; or   when the rotational speed of the motor is greater than a rotational speed threshold, the temperature of the switching transistor in the vertical bridge circuit is not greater than a second temperature threshold, and the terminal voltage of the switching transistor in the vertical bridge circuit is not greater than a second voltage threshold, conduct an upper-half-bridge switching transistor or a lower-half-bridge switching transistor in the vertical bridge circuit; and   when the torque of the motor is less than or equal to a second torque threshold or the current output by the output terminal is less than or equal to a second overcurrent threshold, enable the switching transistor in the vertical bridge circuit.   
     
     
         17 . The power assembly according to  claim 12 , wherein the control apparatus is further configured to:
 after enabling or disabling the switching transistor in the horizontal bridge circuit, adjust a duty cycle of a pulse width modulation control signal, so that a voltage output by the output terminal remains unchanged.